Cooling Apparatus of Looped Heat Pipe Structure

ABSTRACT

A coolant phase changeable cooling apparatus using a capillary action is provided. The cooling apparatus prevents a generation of bubbles inside a wick of an evaporator or an inverse flow of a vaporized gaseous coolant through a wick. Also, a thermal contact area can be widened by using at least one groove of a gaseous coolant flow passage unit. Based on these provided effects, cooling efficiency of the cooling apparatus can be improved.

TECHNICAL FIELD

The present invention relates to a coolant phase changeable cooling apparatus using a capillary action, and more particularly, to a cooling apparatus which widens heat contact areas of a porous member, into which a liquid coolant is filled by adhesiveness of an internal capillary tube of an evaporator, and the filled liquid coolant and includes a groove which gives fluidity of a vaporized coolant.

BACKGROUND ART

As the integration scale of semiconductor devices has been increased, a higher level of heat has been given off per unit area of a semiconductor chip. This increasing heat emission causes degradation of reliability of a system utilizing semiconductor devices.

Hence, cooling technology has been developed to solve the above disadvantage related to the increasing heat emission. One typical cooling method is to use latent heat of a coolant and is advantageous in respect of cooling efficiency, manufacturing costs and installation spaces. That is, since this cooling method does not generally require a driving source, it is possible to realize minimization due to a simple configuration of a cooling apparatus.

However, according to the above cooling method, circulation of the coolant depends on heat emitted from an external heat emitter. Thus, if heat is not sufficiently absorbed from the external heat emitter when a cooling apparatus first operates, there may be a disadvantage that cooling capability is diminished because of the insufficient operation power for circulating the coolant.

Another cooling method of improving the aforementioned disadvantage is the use of a capillary pumped loop (CPL) type cooling apparatus. The CPL type cooling apparatus utilizes a capillary wick to use a surface tension of the coolant as the operation power for circulating the coolant.

When designing an evaporator of the CPL type cooling apparatus, it is considered important to have an appropriate discharge structure which quickly transfers a gaseous coolant vaporized as absorbing heat from an emitting body to a condenser and to install an appropriate wick which re-supplies a liquid coolant by generating a capillary action for the purpose of preventing an incidence of dry-out occurring when the coolant is dried out when the liquid coolant stops flowing inside the evaporator.

Examples of a porous material used as a conventional wick are metal-based substances such as nickel, titanium and copper, synthetic resin-based substances such as polypropylene (PP) and polyethylene (PE) and ceramic-based substances.

However, this improved conventional cooling method still has limitations. In the case that such metal-based substance is used, vapor is more likely to flow inversely because the coolant is vaporized even at a part of the evaporator into which the liquid coolant flows due to high thermal conductivity of the metal-based substance. The inverse flow may cause a decrease in the thermal transfer efficiency of the cooling apparatus and increase the manufacturing costs.

The synthetic resin-based substance has a low ignition point and a high degree of thermal transformation and thus, the latter mentioned conventional cooling method may not be used when a brazing process is performed for fabricating an evaporator.

Despite that the ceramic-based substance has good thermal conductivity and adhesiveness, if a ceramic wick is not cooled off gradually after being heated at high temperature for installing the ceramic wick inside a housing and joining the ceramic wick with the housing during fabricating the evaporator, the ceramic wick may be easily broken off due to different thermal expansion coefficients between the ceramic wick and the housing.

DISCLOSURE OF THE INVENTION

It is, therefore, an object of the present invention to provide a cooling apparatus with a looped heat pipe structure which improves a cooling function by preventing a generation of bubbles inside a wick of an evaporator or an inverse flow of a vaporized gaseous coolant through the wick.

It is another object of the present invention to provide a cooling apparatus with a looped heat pipe structure which causes vaporization of a liquid coolant by forming a microgroove or a porous member in a gaseous coolant flow passage unit.

In accordance with one aspect of the present invention, there is provided a cooling apparatus with a looped heat pipe structure, including: an evaporator including a housing having at least one liquid coolant inlet and at least one gaseous coolant outlet and an inner structure and discharging a coolant to said at least one gaseous coolant outlet by vaporizing the coolant flowed into said at least one liquid coolant inlet through absorbing heat from a heat emitter; a gaseous coolant flow passage unit including at least one groove formed nearly in parallel on an inner wall of the evaporator at a heat emitter contact unit side such that said at least one groove is connected with said at least one gaseous coolant outlet and a chamber unit formed at one edge side of said at least one groove; a condenser including an inlet connected with said at least one gaseous coolant outlet and an outlet connected with said at least one liquid coolant inlet; at least one gaseous coolant pipe and at least one liquid coolant pipe, each one edge is connected with the evaporator and another edge is connected with the condenser to transfer the coolant; and a porous member disposed between said at least one liquid coolant inlet and the gaseous coolant flow passage unit, wherein the porous member includes one of a single structure of a first porous member based on an activated carbon fiber and a multiple structure including the first porous members disposed at both sides of a second porous member based on a ceramic material.

The cooling apparatus further includes a third porous member disposed between the gaseous coolant flow passage unit and the porous member and having thermal conductivity same as or larger than the housing.

Said at least one groove of the gaseous coolant flow passage unit may include a plurality of microgrooves or at least one portion on which a porous member is formed.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and aspects of the invention will become apparent from the following description of the embodiments with reference to the accompanying drawings, in which:

FIG. 1 is a perspective view showing a cooling apparatus with a looped heat pipe structure in accordance with a specific embodiment of the present invention;

FIG. 2 is an exploded perspective view showing an encasing of a first porous member inside an evaporator in accordance with the specific embodiment of the present invention;

FIG. 3 is an exploded perspective view showing another encasing of a second porous member inside an evaporator in accordance with another specific embodiment of the present invention;

FIG. 4 is an exploded perspective view showing a further encasing of a third porous member inside an evaporator in accordance with a further specific embodiment of the present invention;

FIG. 5 is an exploded perspective view showing another embodied housing of an evaporator in accordance with the present invention;

FIG. 6 shows a front view, a top view and a right side view of grooves formed on a housing of the evaporator in accordance with the specific embodiment of the present invention;

FIG. 7 is a cross-sectional view showing grooves formed on inner surfaces of the housing of the evaporator in accordance with the specific embodiment of the present invention;

FIG. 8 shows cross-sectional views of variously embodied groove shapes in accordance with the present invention;

FIG. 9 is a partial perspective view showing a liquid coolant pipe in accordance with the specific embodiment of the present invention;

FIG. 10 shows cross-sectional views of variously embodied liquid coolant pipes in accordance with the present invention; and

FIG. 11 is a perspective view exposing a partially cut portion to show how the liquid coolant pipe is inserted into the evaporator in accordance with the specific embodiment of the present invention.

DESCRIPTION OF THE PRINCIPAL REFERENCE NUMERALS

-   -   100: evaporator     -   110: housing     -   111: front housing     -   113: rear housing     -   121: body     -   123: top lid     -   125: bottom lid     -   115: liquid coolant inlet     -   117: gaseous coolant outlet     -   130: gaseous coolant flow passage unit     -   131: groove     -   133: chamber unit     -   135: microgroove     -   137: porous member     -   150: first porous member     -   170: second porous member     -   190: third porous member     -   200: condenser     -   210: inlet     -   230: radiation unit     -   250: outlet     -   270: liquid coolant storage unit     -   300: liquid coolant pipe     -   310: penetration opening     -   330: microgroove     -   350: porous member     -   400: gaseous coolant pipe

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, a cooling apparatus of a looped heat pipe structure in accordance with certain embodiments of the present invention will be described in detail with reference to the accompanying drawings. Also, it should be noted that the same reference numerals are used for the same configuration elements even in different drawings.

FIG. 1 is a perspective view showing a cooling apparatus with a looped heat pipe structure in accordance with a specific embodiment of the present invention.

As shown, the cooling apparatus includes: an evaporator 100 disposed closely to a heat emitter which is a high temperature unit; a condenser 200 disposed at a low temperature unit side; at least one gaseous coolant pipe 400 connecting at least one gaseous coolant outlet 117 of the evaporator 100 with at least one inlet 210 of the condenser 200; at least one liquid coolant pipe 300 connecting at least one outlet 250 of the condenser 200 with at least one liquid coolant inlet 115 of the evaporator 100; and a coolant filled inside the cooling apparatus and circulating while being transformed into a gaseous state and a liquid state.

FIG. 2 is an exploded perspective view showing an encasing of a first porous member 150 inside the evaporator 100 in accordance with the specific embodiment of the present invention.

It is preferable not to deteriorate micropenings of the porous member used as a wick or cause a volume change when the wick is installed inside a housing 110 and then jointed together at high temperature. As illustrated in FIG. 2, the housing 110 can include a front housing 111 and a rear housing 113.

As for the joining of the housing 110, a brazing method is generally used. For instance, in the case that the housing 110 includes aluminum (Al), the brazing is carried out at a temperature ranging from approximately 500° C. to approximately 650° C. In the case that the housing 110 includes copper (Cu), the brazing temperature increases up to approximately 1,000° C. Also, depending on a material used for the housing 110, a higher brazing temperature may be required. Therefore, an activated carbon fiber used in the specific embodiment of the present invention preferably has a porous structure and a volume that does not change in a greater extent, so that a certain level of a capillary action can occur at such a range of the brazing temperature.

The activated carbon fiber used for the porous member is commonly used as an absorbent, which is employed for adsorbing an organic solvent, filtering the air and water, removing bad odor, and forming gas masks. Since activated carbon has a large specific surface area but the size of a micropenings is relatively wide being in a range of approximately 2 Å to approximately 2,000 Å and, is formed in a powder or grain type, a greater processing effort is required to have a desired shape of the activated carbon. In contrast, the activated carbon fiber has approximately 10 Å to approximately 20 Å of uniform micropenings and thus, the activated carbon fiber has a good absorption capability and a faster absorption rate. The absorption rate of the activated carbon fiber is faster than that of the conventional activated carbon by approximately 10-fold to approximately 100-fold and, the absorption capability of the activated carbon fiber is greater than that of the conventional activated carbon by approximately 2-fold to several tens-fold.

Because of the above described characteristics of the activated carbon fiber, the activated carbon fiber is considered as an appropriate material for the porous member, i.e., the wick, which transfers a liquid coolant by using the capillary action. Since the diameters of the micropenings are very small, vaporized bubbles are generated or transferred with difficulty while the liquid coolant is being absorbed. Since the thermal conductivity of the activated carbon fiber is very low, it is possible to minimize an incidence of inverse thermal conductivity.

As for a material for the first porous member 150 having the above characteristics, it is unnecessary to limit specific values indicating material characteristics such as an absorption value of iodine or benzene. Empirically, it is preferable to use an activated carbon fiber with an absorption value of iodine ranging from approximately 100 mg/g to approximately 5,000 mg/g or an absorption value of benzene ranging from approximately 20 weight percent (wt %) to approximately 80 wt %.

The first porous member 150 including activated carbon fibers is a fiber-based material. When a portion of the first porous member 150 is cut and implemented according to the specific embodiment of the present invention, a function of the first porous member 150 is degraded due to raveled fibers or partially ripped fibers. Even if a portion of the activated carbon fibers is formed in the shape of prominences and depressions, the same disadvantage occurs.

Therefore, instead of forming the first porous member 150 of which portion is partially removed or in the shape of prominences and depressions, the first porous member 150 is preferably formed in the shape of blocks. In the latter case, it is preferable to form the block shape corresponding to the shape of the evaporator 100.

As for another embodiment of the porous member, a second porous member 170 including a ceramic material can be used along with the first porous member 150 including the activated carbon fibers. A conventionally employed ceramic wick has good adhesiveness and low thermal conductivity; however, the ceramic wick may be easily broken off during the joining operation for the evaporator 100. As illustrated in FIG. 3, the second porous member 170 is preferably placed in between the fist porous members 150, so that the second porous member 170 can be blocked from directly contacting the housing 110 of the evaporator 100.

There are several advantages when using the second porous member 170 based a ceramic material in addition to the first porous member 150 based on activated carbon fibers. First, since the first porous member 150 placed at both sides of the second porous member 170, the second porous member 170 does not make a direct thermal contact with the housing 110. Thus, it is possible to prevent potential damages occurring during the joining operation of the housing 110. Second, the second porous member 170 blocks an inverse flow of the coolant from a gaseous coolant flow passage unit 130 to said at least one liquid coolant pipe 300. Third, since activated carbon fibers have a property of elasticity, the activated carbon fibers are stretched at high pressure, and thus, vapor may pass through gaps between stretched fibers. This incidence is commonly called ‘back flow’. Hence, using the second porous member 170 including a non-fiber based material, e.g., a ceramic material, prevents the back flow incidence.

Also, it is preferred that the first porous member 150 and the second porous member 170 have a level of thermal conductivity lower than a material for the housing 110 of the evaporator 100.

As for a further embodiment of the porous member, a third porous member 190 having the same as or higher thermal conductivity than the housing 110 may be further placed. As illustrated in FIG. 4, the third porous member 190 is preferably placed between the gaseous coolant flow passage unit 130 and the first porous member 150 and more specifically, the third porous member 190 is preferably placed on protruded portions of the gaseous coolant flow passage unit 130.

The third porous member 190 has larger micropenings compared with the first porous member 150 and includes a material selected from a group consisting of metal mesh with high thermal conductivity, sintered metal powder, an etched metal plate, and a Cu-based metal with high thermal conductivity.

The third porous member 190 widens a surface area where the liquid coolant is vaporized as the third porous member 190 receives heat through the housing 110 of the evaporator 100 and simultaneously makes the liquid coolant transferred through the first porous member 150 flow more easily.

As described above, a single structure of the first porous member 150, a structure obtained by placing the second porous member 170 in between the first porous members 150, a structure obtained by sequentially arranging the third porous member 190 and the first porous member 150, and a structure obtained by sequentially arranging the third porous member 190, the first porous member 150, the second porous member 170, and the first porous member 150 are also possibly formed on the gaseous coolant flow passage unit 130.

FIG. 5 is an exploded perspective view showing a housing of an evaporator in accordance with another specific embodiment of the present invention. FIG. 6 shows front, top and right side views of grooves formed within the housing 110 of the evaporator 100 in accordance with the specific embodiment of the present invention. FIG. 7 is a cross-sectional view showing grooves formed on inner sidewalls of the housing 110 of the evaporator 100 in accordance with the specific embodiment of the present invention.

As shown in FIG. 2, the housing 110 of the evaporator 100 includes: the front housing 111 where the gaseous coolant flow passage unit 130 is formed on an inner wall of the front housing 111 at a heat emitter contact unit side; at least one liquid coolant inlet 115; at least one gaseous coolant outlet 117; and the rear housing 113 joined with the front housing 111 in a manner to have a space where the porous member is encased inside the housing 110.

As another embodiment of the housing 110 of the evaporator 100, the housing 110 can further include a body including the gaseous coolant flow passage unit 130 formed on the inner wall at the heat emitter contact unit side and at least one lid combined with at least one surface of the body.

FIG. 5 shows that the housing 110 can include: a body 121 encasing a porous member; and a top lid 123 and a bottom lid 125 combined with a top surface and a bottom surface of the body 121, respectively.

The shape of the evaporator 100 can be formed variously depending on the shape of a heat emitter. It is preferable to have a structure that does not allow an inverse flow of a vaporized gaseous coolant from the evaporator 100 to said at least one liquid coolant inlet 115 through the porous member.

The housing 110 of the evaporator 100 is formed through a joining operation. Among various processes, soldering, brazing, or welding can be possibly employed as the joining method for maintaining the inner side of the evaporator 100 in vacuum. Preferably, the joining method is selected in consideration of an employed material for the housing 110, a maximum operation temperature of the cooling apparatus, vaporization pressure of the coolant, and cost-effectiveness. Generally, the soldering or brazing is mainly utilized.

The soldering and the brazing coat a filler metal between base metals to be joined together and apply a certain range of heat that is higher than a melting point of the filler metal but lower than the melting points of the base metals thereon, thereby joining the two base metals together. If the heating temperature is lower than approximately 450° C., the soldering is employed, and if the heating temperature is higher than approximately 450° C., the brazing is employed.

In the case that a wick is placed inside the housing 110 and joined together, the joining process should be carried out carefully not to cause a collapse of a porous structure including a single porous member or multiple porous members during the joining process at high temperature or not to cause an overall shape or volume change. Thus, as described above, the porous member should not have changes in the sizes of the micropenings, the overall shape or the volume.

As illustrated in (d) of FIG. 7, at least one inner wall of the housing 110 of the evaporator 100 is protruded towards the inner side of the evaporator 100 in the form of a convex. That is, the housing 110 has at least one curved inner wall to distribute heat from the heat emitter throughout the housing 110. Although it is common to form the curved inner wall at the heat emitter contact unit side, other inner walls can also be curved, whereby thermal transfer efficiency can be improved.

The gaseous coolant flow passage unit 130 serves a role in discharging the gaseous coolant generated as the liquid coolant absorbed on the porous member makes a thermal contact with the housing 110 to said at least one gaseous coolant outlet 117. Also, the gaseous coolant flow passage unit 130 widens the thermal contact area with the liquid coolant, so that a large amount of the liquid coolant is changed into a gaseous state.

As shown in (a) of FIG. 6, the gaseous coolant flow passage unit 130 includes at least one groove 131 formed nearly in parallel on the inner sidewall of the front housing 111 contacting to the heat emitter. Also, as shown in FIG. 11, the gaseous coolant flow passage unit 130 also includes a chamber unit 133 with which one end of the groove 131 is joined. As (a) of FIG. 6 illustrates, it is preferable to have a number of the grooves 131.

Forming a plurality of microgrooves 135 on the individual groove 131 of the gaseous coolant flow passage unit 130 or a porous member 137 on a portion of the individual groove 131 can improve cooling efficiency. The reason for this result is because a filling rate of the liquid coolant into the individual groove 131 by a capillary action increases. Also, the cooling efficiency increases due to a smooth exchange of potential heat as the thermal contact area of the liquid coolant becomes widened.

The gaseous coolant flow passage unit 130 is formed to be connected with said at least one gaseous coolant outlet 117 for the purpose of smoothly transferring the vaporized gaseous coolant to said at least one gaseous coolant outlet 117. Thus, it is preferable to dispose said at least one gaseous coolant outlet 117 of the evaporator 100 at a position corresponding to the chamber unit 131 of the gaseous coolant flow passage unit 130.

The grooves 131 of the gaseous coolant flow passage unit 130 can be formed in a lattice structure and this lattice structure of the grooves 131 is shown in (b) of FIG. 6.

As illustrated in (c) of FIG. 7, the gaseous coolant flow passage unit 130 can be formed only on the inner sidewall of the housing 110 at the heat emitter contact unit side. As shown in (a), (b) and (d), it is also possible to form the gaseous coolant flow passage unit 130 on at least one another inner sidewall.

FIG. 8 is a cross-sectional view showing variously embodied grooves of the evaporator 100 in accordance with the present invention.

The cross-sectioned shape of the individual groove 131 of the gaseous coolant flow passage unit 130 can be embodied in various shapes to widen the thermal contact area and to quickly transfer the vaporized gaseous coolant. FIG. 8 shows the grooves 131 embodied in circular, triangular, reverse triangular and rectangular shapes.

Typical grooves 131 without including a porous member is shown in (a) of FIG. 8. A partial number of the grooves 131 of the evaporator 100 can include the porous member.

The section (b) of FIG. 8 shows the above case of forming the partial number of the grooves with the porous member, while the section (c) of FIG. 8 shows the case of forming the entire grooves with the porous member. Herein, the porous member is based on a material selected from a group consisting of metal mesh, sintered metal powder and an etched metal plate.

The section (d) of FIG. 8 shows that a plurality of microgrooves are further formed on the individual groove 131.

As illustrated in (b) of FIG. 8, in the case that a partial number of the grooves 131 include the porous member, those microgrooves can be formed on those grooves without including the porous member.

FIG. 9 is a partial perspective view showing the liquid coolant pipe 300 in accordance with the specific embodiment of the present invention. FIG. 10 shows various embodiments of the liquid coolant pipe 300 in accordance with the present invention. The liquid coolant pipe 300 illustrated in FIG. 9 includes a plurality of penetration openings 310 and microgrooves.

When an air bubble generated inside the evaporator 100 or an inversely flowing liquid coolant is flowed into the liquid coolant pipe 300, the penetration openings 310 discharge the air bubble or the inversely flowing liquid coolant to the inner side of the evaporator 100 by the liquid coolant flowing from the condenser 200 to the evaporator 100.

Preferably, the plurality of penetration openings 310 are formed at a bottom part of the liquid coolant pipe 300 inserted into the porous member encased into the housing 110. At least one row of the multiple penetration openings 310 is preferably formed. As shown in FIG. 2, at least one opening is preferably formed on one surface of the first porous member 150 corresponding to the individual liquid coolant pipe 300 with the multiple penetration openings 310 in such a shape allowing the liquid coolant pipe 300 to be inserted through. If the evaporator 100 is thin, the penetration opening 310 may not be necessary.

FIG. 9 shows that grooves are formed on the inner wall of the liquid coolant pipe 300 in the axial direction. The grooves in the axial direction generate a capillary action transferring the liquid coolant from the condenser 200 to the evaporator 100.

As for an inner structure of the liquid coolant 300, a structure including microgrooves formed on the inner wall in the axial direction (refer to (a) and (b) of FIG. 10), a structure further including a porous member in front of the inner wall where the microgrooves are formed (refer to (c) and (d) of FIG. 10) or a structure including a porous member in front of the inner wall where the microgrooves are not formed (refer to (e) of FIG. 10) is preferably formed. The porous member disposed inside the liquid coolant pipe 300 preferably includes a material selected from a group consisting of metal mesh, sintered metal powder and a woven wick.

As shown in FIG. 1, the condenser 200 includes: at least one inlet 210; a radiation unit 230; at least one outlet 250; and a liquid coolant storage unit 270.

The gaseous coolant flowed from the evaporator 100 to the condenser 200 through at least one gaseous coolant pipe 400 connected with said at least one inlet 210 becomes a liquid coolant due to a thermal exchange as the gaseous coolant passes through the radiation unit 230. The liquid coolant is stored into the liquid coolant storage unit 270 at the outlet 250 side and flows into the evaporator 100 through said at least one liquid coolant pipe 300 connected with said at least one outlet 250.

As another embodiment of the condenser 200, the condenser 200 is placed at the upper side of the evaporator 100 in the case that the coolant does not circulate smoothly due to the insufficient capillary action of the individual liquid coolant pipe 300. This specific arrangement of the condenser 200 makes the liquid coolant collected at the liquid coolant storage unit 270 be smoothly transferred to the evaporator 100 by using the gravitational force.

To increase heat radiation efficiency of the radiation unit 230 of the condenser 200, a fan may be installed at one side of the condenser 200 or the condenser 200 may be combined with a cooling water circulation device.

FIG. 11 is a perspective view exposing a partially cut portion of the cooling apparatus to show how the individual liquid coolant pipe 300 is inserted into the evaporator 100 in accordance with the specific embodiment of the present invention. With reference to FIG. 11, operation of the cooling apparatus with the looped heat pipe structure will be described in detail.

The liquid coolant flows into the inner side of the evaporator 100 by a capillary action generated by the microgrooves 330 formed on the inner sidewall of the individual liquid coolant pipe 300 in the axial direction. The liquid coolant flows into the first porous member 150 encased inside the evaporator 100. The first porous member 150 generates a capillary action to make the liquid coolant be swiftly transferred to the gaseous coolant flow passage unit 130 before the liquid coolant is vaporized. The liquid coolant arrived at the gaseous coolant flow passage unit 130 is vaporized through a thermal contact. The vaporized gaseous coolant is transferred to the chamber unit 133 through the individual groove 131 of the gaseous coolant flow passage unit 130. The individual gaseous coolant pipe 400 is formed at a position corresponding to the chamber unit 133 through which the gaseous coolant is transferred to the condenser 200.

EFFECT OF THE INVENTION

In accordance with certain embodiments of the present invention, a cooling apparatus with a looped heat pipe structure utilizes activated carbon fibers. Also, the cooling apparatus is provided with an effect of increasing a capillary action with low costs. By using a ceramic-based or metal-based porous member along with the fiber-based porous member, it is possible to enhance cooling efficiency. Also, vaporization of a coolant can be accelerated by forming microgrooves or a porous member on the individual groove. It is further possible to accelerate a circulating transfer of the liquid coolant by forming microgrooves or a porous member on sidewalls of the individual liquid coolant pipe.

Although the preferred embodiments of the invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 

1. A cooling apparatus with a looped heat pipe structure, comprising: an evaporator including a housing having at least one liquid coolant inlet and at least one gaseous coolant outlet and an inner structure and discharging a coolant to said at least one gaseous coolant outlet by vaporizing the coolant flowed into said at least one liquid coolant inlet through absorbing heat from a heat emitter; a gaseous coolant flow passage unit including at least one groove formed nearly in parallel on an inner wall of the evaporator at a heat emitter contact unit side such that said at least one groove is connected with said at least one gaseous coolant outlet and a chamber unit formed at one edge side of said at least one groove; a condenser including an inlet connected with said at least one gaseous coolant outlet and an outlet connected with said at least one liquid coolant inlet; at least one gaseous coolant pipe and at least one liquid coolant pipe, each one edge is connected with the evaporator and another edge is connected with the condenser to transfer the coolant; and a porous member disposed between said at least one liquid coolant inlet and the gaseous coolant flow passage unit, wherein the porous member includes one of a single structure of a first porous member based on an activated carbon fiber and a multiple structure including the first porous members disposed at both sides of a second porous member based on a ceramic material.
 2. The cooling apparatus of claim 1, wherein one of the first porous member and the second porous member has a low level of thermal conductivity than the housing.
 3. The cooling apparatus of claim 1, wherein the activated carbon fiber includes at least one opening on one surface of the activated carbon fiber, so that at least one liquid coolant pipe is inserted through, and said at least one liquid coolant pipe includes a plurality of penetration openings on one edge portion which is inserted into the activated carbon fiber.
 4. The cooling apparatus of claim 1, further including a third porous member disposed between the gaseous coolant flow passage unit and the porous member and having thermal conductivity same as or larger than the housing.
 5. The cooling apparatus of claim 4, wherein the third porous member includes a material selected from a group consisting of metal mesh, sintered metal powder and an etched metal plate.
 6. The cooling apparatus of claim 1, wherein the housing of the evaporator includes: a front housing in which the gaseous coolant flow passage unit is formed on the inner wall at the heat emitter contact unit side; and a rear housing including said at least one liquid coolant inlet and said at least one gaseous coolant outlet and joined with the front housing in a manner to create a space encasing the porous member inside the housing.
 7. The cooling apparatus of claim 1, wherein the housing of the evaporator includes: a body including the gaseous coolant flow passage unit formed on the inner wall at the heat emitter contact unit side; and at least one lid joined with at least one surface of the body.
 8. The cooling apparatus of claim 6 or 7, wherein the housing of the evaporator includes at least one inner sidewall formed in a curvature structure protruded towards an inner side of the evaporator.
 9. The cooling apparatus of claim 6 or 7, wherein the gaseous coolant flow passage unit is formed at least one another inner wall of the housing in addition to the inner wall of the housing at the heat emitter contact unit side.
 10. The cooling apparatus of claim 6 or 7, wherein said at least one groove of the gaseous coolant flow passage unit is formed in a lattice structure.
 11. The cooling apparatus of claim 6 or 7, wherein said at least one groove of the gaseous coolant flow passage unit includes a plurality of microgrooves.
 12. The cooling apparatus of claim 6 or 7, wherein said at least one groove of the gaseous coolant flow passage unit includes at least one portion on which a porous member is formed.
 13. The cooling apparatus of claim 12, wherein the porous member formed on said at least one groove includes a material selected from a group consisting of metal mesh, sintered metal powder and an etched metal plate.
 14. The cooling apparatus of claim 1, wherein the condenser includes a liquid coolant storage unit storing the coolant liquefied as being thermally radiated at the condenser and disposed at said at least one outlet side.
 15. The cooling apparatus of claim 1 or 3, wherein the inner structure of said at least one liquid coolant pipe includes one structure selected among a structure including microgrooves formed on an inner wall of said at least one liquid coolant pipe in the axial direction, a structure further including a porous member disposed in front of the inner wall on which the microgrooves are formed and a structure including the porous member in front of an inner wall on which the microgrooves are not formed.
 16. The cooling apparatus of claim 15, wherein the porous member disposed inside at least one liquid coolant pipe includes a material selected from a group consisting of metal mesh, sintered metal powder and a woven wick. 